The present invention relates to a porous structure superior in water repellency, an ink-jet recording head, a method of manufacturing those, and an ink-jet recording apparatus.
Water repellency treatment is performed for preventing drop adhesion or for preventing contamination. Various water repellents and water repellency treatments have been developed and used in various products including electronic equipment. Particularly, in an ink-jet recording apparatus, water repellency treatment has been put to practical use as surface treatment of a head which is the heart of the ink-jet recording apparatus. The water repellency treatment is an important treatment influencing printing quality.
Glass, metal, etc. is used as a constituent material component of an ink ejecting surface of an ink-jet recording head. When water-based or oil ink is used in an ink-jet recording head, drops of the ink are apt to adhere to a nozzle surface under the conditions that the water repellency of the nozzle surface is not sufficient. As a result, straight shooting of ejected ink drops is hindered to cause a trouble such as printing turbulence or the like to thereby occasionally affect long-term reliability. In addition, the constituent material of the ink ejecting surface of the ink-jet recording head is characteristically apt to get wet with ink. Therefore, water repellency treatment is given to the ink ejecting surface in order to perfectly prevent water based or oil ink from adhesion.
As for such water repellency treatment, there is a water repellency treatment (super-water-repellency treatment) ideal for an ink-jet recording head, in which the contact angle of water exceeds 120 degrees. As mentioned in xe2x80x9cIntroduction to Fluorochemistryxe2x80x9d, THE NIKKAN KOGYO SHINBUN LTD., published Mar. 1, 1997, from line 10 of p.59 to line 6 of p.63, known is an eutectoid plating method in which polyfluoroethylene particles increased in fluorine atom density are dispersed in nickel film, or a coating method in which such a surface shape as trade name xe2x80x9cKanpenirexxe2x80x9d by KANSAI PAINT CO., LTD. is designed to realize super-water-repellency.
However, conventional super-water-repellency treatment methods have problems as follows.
(1) Various surface active agents are added to ink for an ink-jet recording apparatus in order to make pigment disperse stably and permeate paper. In the eutectoid plating method, these surface active agents are absorbed into the nickel surface, so that the quality of the nickel surface may be lowered by ink wetting in long-term printing.
(2) In an ink-jet recording apparatus, a rubbing operation with rubber is required for cleaning paper powder or foreign contamination adhering to the head surface. In the conventional super-water-repellency coating methods, coating may peel off through this operation, so that the quality of the head surface may be lowered.
The present invention has been made to solve the foregoing problems. It is an object of the present invention to provide a porous structure in which water repellency is kept for a long term; an ink-jet recording head with a nozzle surface superior in water repellency properties to maintain high printing quality over a long term; a method of manufacturing such a porous structure and such an ink-jet recording head; and an ink-jet recording apparatus equipped with such an ink-jet recording head.
(1) The porous structure according to the present invention consists of desired protrusion portions and recess portions formed on a surface of a substrate, heights of the protrusion portions on the surface being made uniform. Incidentally, a height of a protrusion portion formed on a substrate is defined as a level of the top surface of the protrusion portion in the direction of thickness of the substrate, in this invention.
(2) In the porous structure according to the above paragraph (1), differences in heights of the protrusion portions are within 250 xcexcm.
(3) In the porous structure according to the above paragraph (1), differences in heights of the protrusion portions are within 15 xcexcm.
(4) In the porous structure according to the above paragraph (1), differences in heights of the protrusion portions are within 5 xcexcm.
(5) The porous structure according to the present invention consists of desired protrusion portions and recess portions formed on a surface of a substrate, a depth of the recess portions on the surface being not smaller than a predetermined value.
(6) In the porous structure according to the above paragraph (5), the depth of the recess portions is not smaller than 1 xcexcm.
(7) In the porous structure according to the above paragraph (5), the depth of the recess portions is not smaller than 3 xcexcm.
(8) In the porous structure according to the above paragraph (5), the depth of the recess portions is not smaller than 5 xcexcm.
(9) The porous structure according to the present invention consists of desired protrusion portions and recess portions formed on a surface of a substrate, and has such a size that liquid drops do not fall down into the recess portions, and the liquid drops can surely contact with an air layer in the recess portions.
(10) In the porous structure according to the above paragraph (9), widths of the protrusion portions or the recess portions is between 0.2 xcexcm and 500 xcexcm.
(11) In the porous structure according to the above paragraph (9), widths of the protrusion portions or the recess portions is between 0.5 xcexcm and 30 xcexcm.
(12) In the porous structure according to the above paragraph (9), widths of the protrusion portions or the recess portions is between 1 xcexcm and 10 xcexcm.
(13) In the porous structure according to the above paragraph (1), (5) or (9), a water repellant film is formed on the substrate having the protrusion portions and recess portions.
(14) In the porous structure according to the above paragraph (1), (5) or (9), the protrusion and recess portions comprises protrusion portions which are disposed distributively or in the form of stripes or a lattice.
(15) In the porous structure according to the above paragraph (1), (5) or (9), the substrate is of silicon, silicon oxide, or glass.
(16) The ink-jet recording head according to the present invention has water repellency performance given to an ink ejecting surface, wherein the ink ejecting surface except ink ejecting holes is constituted by the porous structure defined in the above paragraphs (1), (5) or (9).
(17) The ink-jet recording head according to the present invention has water repellency performance given to an ink ejecting surface, wherein the ink ejecting surface except ink ejecting holes is constituted by the porous structure defined in the above paragraph (9).
(18) In the method of manufacturing a porous structure according to the present invention, the porous structure defined in the above paragraphs (1), (5) or (9) is manufactured by a photolithography method and an etching method.
(19) In the method of manufacturing a porous structure according to the above paragraph (18), the etching method is a trench dry etching.
(20) In the method of manufacturing a porous structure according to the above paragraph (18), the etching method is an anode electrolysis method.
(21) In the method of manufacturing a porous structure according to the above paragraph (18), the etching method is an isotropic wet etching method.
(22) In the method of manufacturing a porous structure according to the above paragraph (18), the etching method is an anisotropic wet etching method.
(23) In the method of manufacturing a porous structure according to the above paragraph (18), the etching method is an isotropic dry etching method.
(24) In the method of manufacturing an ink-jet recording head according to the present invention, the porous structure defined in the above paragraph (16) is manufactured by a photolithography method and an etching method.
(25) In the method of manufacturing an ink-jet recording head according to the above paragraph (24), the etching method is a trench dry etching method.
(26) In the method of manufacturing an ink-jet recording head according to the above paragraph (24), the etching method is an anode electrosis method.
(27) In the method of manufacturing an ink-jet recording head according to the above paragraph (24), the etching method is an isotropic wet etching method.
(28) In the method of manufacturing an ink-jet recording head according to the above paragraph (24), the etching method is an anisotropic wet etching method.
(29) In the method of manufacturing an ink-jet recording head according to the above paragraph (24), the etching method is an isotropic dry etching method.
(30) The ink-jet recording apparatus according to the present invention has such an ink-jet recording head as defined in the above paragraph (16).
(31) The ink-jet recording apparatus according to the present invention has such an ink-jet recording head as defined in the above paragraph (17).
As described above, according to the present invention, a function of water repellency is obtained by a porous structure having a shape of protrusion-and-recess formed artificially on a surface of a substrate. Accordingly, superior properties of water repellency can be kept for a long term.
In addition, according to the present invention, an ink ejecting surface of an ink-jet recording head expect for ink ejecting holes is made to be such a porous structure. Accordingly, the water repellency performance to ink is improved. As a result, printing quality is superior for a long term.
Incidentally, water repellency performance in the present invention includes oil repellant performance.
Further, according to the present invention, the porous structure is manufactured by a photolithography method and an etching method. Accordingly, it is possible to manufacture a super-water-repellency structure having reproducibility.